Brazing solder

ABSTRACT

The invention relates to brazing solders applied for brazing parts made of steel, cast iron, copper and nickel alloys, as well as of noble metals and alloys having their melting point lying above 800* C. The invention is characterized in that the brazing solder proposed therein, has the following weight percent composition: Cu, 20-65; Mn, 15-35, Ag, 15-25; and Ni, 5-20; Zn, 0-15.

United States Patent Novikov et al.

[ 51 Sept. 26, 1972 I BRAZING SOLDER [22] Filed: Nov. 17, 1970 [21]Appl. N0.: 90,452

[52] U.S. Cl ..29/504, 75/134 C, 75/159, 75/161 [51] Int. Cl. ..B23k31/02 [58] Field of Search.....75/l34 C, 134 N, 134 R, 159,

[56] References Cited UNITED STATES PATENTS 3,577,234 5/1971 Boughton etal. ..75/159 FOREIGN PATENTS OR APPLICATIONS 1,792 7/1861 Great Britain..75/134 C Primary ExaminerL. Dewayne Rutledge Assistant Examiner-4. E.Legru Attorney-Waters, Roditi, Schwartz & Nissen [5 7 ABSTRACT Theinvention relates to brazing solders applied for brazing parts made ofsteel, cast iron, copper and nickel alloys, as well as of noble metalsand alloys having their melting point lying above 800 C.

The invention is characterized in that the brazing solder proposedtherein, has the following weight percent composition: Cu, 20-65; Mn,15-35, Ag, l5-25; and-Ni, 5-20; Zn, 0-15.

5 Claims, No Drawings BRAZING SOLDER This invention relates to hard orbrazing solders for brazing articles made of steel, cast iron, copperand nickel, as well as of noble metals and alloys having their meltingpoint above 800 C.

The most extensively used solder for brazing the aforementioned metals,particularly stainless steels including high-strength ones, is a brazingsolder of the following composition: Ag, 92 percent; Cu, 7.5 percent;and Li, 0.2-0.5 percent which contributes to preservation of adequatemechanical characteristics of brazed metals and obtaining brazed jointsable to withstand corrosion attack under any climatic conditions.

l-lowever,said currently employed brazing solder is highly expensive dueto the considerable silver content therein. Application of said solderunder mass production schedule at high consumption rate thereof perarticle produced entails a considerable consumption of silver which isuneconomical.

Moreover, when brazing high-strength steels alloyed with aluminum,chromium and titanium with said solder to provide good wettability andspreadability thereof, requires the use of shielding atmospherefeaturing a high degree of freedom from oxygen and moisture, as well asthe employment of the gaseous fluor-containing brazing fluxes.Purification of shielding atmosphere (commercially pure argon or helim)from oxygen is attained by using oxygen absorbents such as hot titaniumor zirconium sponge, said atmosphere is freed of moisture by means ofsilica gel, both said absorbents and said silica gel being arrangedacross in the flow path of shielding gases.

Thus, the application of said conventional brazing solder makes the costof brazed parts considerably higher and complicates the technologicalprocedure of brazing. Besides, the residual fluor-containing fluxes areimpossible to eliminate from the surface of the parts brazed in closedor blind spaces said residual fluxes affect adversely thecorrosion-resistance of the metal being brazed and the brazed jointsthereof.

It is an object of the present invention to provide a less expensivebrazing solder possessing the advantageous features of the solder usedcurrently.

Another object of the present invention is to provide a brazing alloy ofthe character set forth above which would not require the use of ashielding atmosphere purifled to a high degree of cleanness, nor the useof gaseous fluor-containing brazing fluxes.

These and other objects are achieved by the provision of a brazingsolder having the following weight percentage composition ranges,according to the invention:

The preferred weight percentage composition range of the brazing solderis as follows:

Up to wt. percent of Zn is expedient to be introduced into thecomposition of said brazing solder.

Incorporating of Zn into the present solder composition conduces to areduced attaching of the metal brazed by the liquid solder anddiminishes the melting point thereof. 1

It is likewise expedient that the following constituents be incorporatedinto the composition of the present solder (in wt. percent):

Si 0.5 max.

P 0.3 max.

B 0.3 max.

Introducing of said components into the herein-disclosed solderincreases the flowability thereof and contributes to a better wetting ofstainless steels alloyed with aluminum, chromium and titanium which areliable to formation of stable oxide films on said steel surface whenheated.

The present invention provides silver consumption to be reduced by onefourth, makes it possible to dispense with the purification of shieldinggases and with the use of gaseous fluor-containing brazing fluxes, andto obtain high-strength brazed joints.

Given below are some examples of using brazing solders made according tothe present invention.

EXAMPLE 1 When brazing with a solder of the following preferable weightpercent composition:

Ni 11 parts made of chromium-nickel stainless steel alloyed withaluminum and titanium, sheet thickness being 1 mm, at a temperature of950 C in the shielding atmosphere of commercially pure argon withoutinvolving brazing fluxes, brazed joints therein are found to haveshearing strength of 34.5 kg/mm at room temperature (20 C) and of 23.5kg/mm at 400 C.

After having stayed within 1 month under tropical climate conditions thebrazed joints show the strength thereof remaining unaffected.

Parts brazed with the conventional solder the strength of brazed jointsis found to be 23 kg/mm at 20 C and 13.0 kg/mm at 400 C.

EXAMPLE 2 When brazing parts under the same conditions as stated inExample 1, with a solder of a composition corresponding to the abovespecified lower limit of weight percentage, viz.,

Ni 5 the brazed joints are found to possess a shearing strength equal to23 kg/mm at 20 C and to 18.5 kg/mm at 400 C.

EXAMPLE 3 When brazing parts under the same conditions as described inExamples 1 and 2 safe for brazing temperature which equals to l,000 C,with a solder having a composition corresponding to above specifiedupper limit of weight percentage, viz.,

Ni the brazed joints are found to possess a shearing strength equal to38.5 kg/mm at 20 C and to 28.5 kg/mm at 400 C.

As it is evident from comparison of the results of Examples 1, 2 and 3the solder of Example 3 has a somewhat higher strength than the soldersof Examples 1 and 2, and because it features a higher brazingtemperature, due to the influence of nickel content therein which isalways practicable for brazing high-strength stainless steels which areintolerant for being heated above the hardening temperature. Therefore,the solders according to this invention as specified in Examples l and 2are recommended for brazing such steels.

Anticorrosive properties of the present brazing solder are ensured dueto the introducing of Ag and Ni thereinto. Therefore, when brazed partshave to be operated under most adverse climatic conditions, e.g., undertorrid climate with a high air humidity or under humid marine climate,it is recommendable to introduce silver according to the upper weightpercentage limit, while the percentage content of Mn in the solder undersuch climatic conditions is recommended to be reduced since manganine isliable to affect the corrosion resistance of the brazed joint. Thecontent of silicon, phosphorus and boron is varied in dependence withwhether the metals being brazed contain elements that are liable to formstable exides thus hampering the spreading of the solder. Thus, forbrazing steels alloyed with chromium, titanium and aluminum, a solder ispreferred to be used containing Si, B and P in the above-specifiedratio, 'whereas for brazing carbon steels, use can be made of a solderdevoid of said components.

Zinc is incorporated for reducing the solder melting point anddiminishing the stackability of the metal being brazed by the liquidsolder. It is employed when brazing thin parts such as steel foil0.03-0.05 mm thick, in which case the use should be made of the soldersspecified in Examples 1 and 2 containing 15 wt. percent of Zn. Whenbrazing same steel foil, but 0.5 mm thick use is made of the abovesolder with a 5 wt. percent additive of Zn, and inthe case of steel foil1 mm thick and over, a zincless solder must be used.

The herein-proposed brazing solder does not differ from the heretoforeused brazing solder in its production technology and in brazingtechnique with it, with the exception of that purifying the shieldinggases from oxygen and moisture; and that the using gaseousfluorcontaining fluxes can be dispensed with, when employing the presentsolder.

What is claimed is:

l. A brazing solder, consisting essentially of:

Cu 20-65 wt. percent Mn 15-35 wt. percent Ag 15-25 wt. percent Ni 5-20wt. percent Zn 0-15 wt. percent 2. A brazing solder consistingessentially of:

Cu 41-49 wt. percent Mn 21-23 wt. percent Ag 20-23 wt. percent Ni 10-13wt. percent Zn O-l 5 wt. percent 3. The brazing solder as claimed incla1m 1, into whose composition are introduced:

Si up to 0.5 wt. percent max.

P up to 0.3 wt. percent max.

B up to 0.3 wt. percent max.

4. A process for brazing steel, cast iron, copper, nickel, noble metalsand alloys thereof said metals and alloys having a melting point above800 C, comprising brazing the metals with a brazing alloy according toclaim 1.

5. The process according to claim 4 wherein the brazing solder includes:

Si up to 0.5 wt. percent max.

P up to 0.3 wt. percent max.

B up to 0.3 wt. percent max.

2. A brazing solder consisting essentially of: Cu 41-49 wt. percent Mn21-23 wt. percent Ag 20-23 wt. percent Ni 10-13 wt. percent Zn 0-15 wt.percent
 3. The brazing solder as claimed in claim 1, into whosecomposition are introduced: Si up to 0.5 wt. percent max. P up to 0.3wt. percent max. B up to 0.3 wt. percent max.
 4. A process for brazingsteel, cast iron, copper, nickel, noble metals and alloys thereof saidmetals and alloys having a melting point above 800* C, comprisingbrazing the metals with a brazing alloy according to claim
 1. 5. Theprocess according to claim 4 wherein the brazing solder includes: Si upto 0.5 wt. percent max. P up to 0.3 wt. percent max. B up to 0.3 wt.percent max.